Process of preparing dihydropterins



Patented June 17, 1952 ,UNITED STATES PATENT OFFICE 2,601,215 I PROCESS OF PREPARING DIHYDROPTERINS Coy W. Waller and John H. Mowat, Pearl ltiver,

N. Y., assignors to American Cyanamid Com.- pany, New York, N. Y., a corporation of Maine No Drawing. Application March 17, 1948, Serial No. 15,488

1 Claim. (01. 260-42515) 1 2 This invention relates to organic compounds 2,4,5-triamino-6-hydroxypyrimidine, or one of possessing biological activity and other useful its tautomers, with one of the several alpha,betaproperties and to processes of preparing the dihalopropionaldehydes, such as alpha,beta-disame. bromopropionaldehyde, alpha,betadichloropro- In our U. S. Patent 2,500,296 issued March pionaldehyde, or one of these compounds in the 14, 1950, of which this is a continuation-in-part, form of its acetal. Also, as in our earlier appliwe disclosed that new organic compounds could cation, we may use as the third reactant be prepared by the reaction of 2,4,5-triaminoaminobenzoic acid or one of its various salts, fi-hydroxypyrimidine, and alpha,beta-dihaloesters, and amides, particularly those amides propionaldehyde, and aminobenzoic acid or salts, 10 of amino acids, such as p-aminobenzoylglutamic esters, and amides thereof. The reaction was acid, p-aminobenzoylaspartic acid, p-aminobenillustrated therein by the following equation: zoyldiglutamylglutamic acid, and the like.

N NH,

XoHcHiX N O NH; NH:

* CH l N N OHiNH- 211K 11.0

in which X is a halogen and R is -OH, -OR,', To prepare the dihydropterins in purer form or NR"R"', B. being an alkyl radical and R" a suitable pterin, such as pteroylglutamic acid, and R' being hydrogen or aliphatic or aromatic pteroyldiglutamylglutamic acid, pteroylaspartic radicals. acid, pteroic acid, or the like, is first prepared As stated therein, two hydrogen atoms of the and then reduced, for example, with platinum pyrazyl ring of the product were removed to yield oxide and hydrogen, zinc dust in alkali, or other compounds possessing useful biological activity, reducing agents which do not carry the reduction for example, pteroic acid, pteroylglutamic acid, beyond the desired dihydro condition. The isoand others. The present application describes in lated crystalline product appears to be quite stagreater particularity dihydropteroic acid and its ble. To be more definite, the following examples salts, esters and amides, which are obtained in of typical reductions and the characteristics of that process as intermediates. the resulting dihydropterin will be given.

In our aforesaid earlier filed application the COR dihydropterins obtained as intermediates were 40 Example 1 oxidized under the conditions of the process and Platinum Oxide mes), 25 cc. of water converted into pteroic acid, esters and amides and three drops of Concentrated hydrochloric thereof without isolation from the reaction mixcid were placed in a reduction hom and t ture. Because of the many by-prod t assocatalyst activated with hydrogen. To this mixciated with the reaction, it is not generally fease Was added a Solution of grams of p oy ible to isolate the dihydropterins from the crude glutamic acid in cc. of .6 N sodium hydroxide, reaction mixture, the principal reasom being The material was then reduced at room temperathat these dihydropterins are readily oxidized ur a d atmospheric pressure- It required about during the purification procedure, particularly in five hours to reduce, during which time approxithe presence of the various by-products of the 50 mately cc. of hydrogen were absorbed. The reaction. We have found that for purposes of calculated amount necessary to reduce the comobtaining the product in a high state of purity it pound to the dihydro form is 153 cc. The mixis better to first obtain pteroic acid or one of ture was then treated with a small amount of its salts, esters, and amides and thereafter recharcoal, filtered, and the filtrate immediately duce this purified material to the desired (11- 55 cooled to 10 C. It was acidified to pH 2.7, hydro form, cooled for thirty minutes, centrifuged, washed To obtain the dihydropteroic acid and its salts, with water, methanol and ether, and dried; yield esters, and amides of the present invention in 2.65 grams. crude form we carry out the reaction described This material was purified as follows: 1.75 above under non-oxidiaing conditions using 69 grams of the product were dissolved in 20 3 of ice-cold concentrated hydrochloric acid, treated with about .5 gram of charcoal, and filtered. The charcoal was washed with 3 cc. of concentrated hydrochloricacid, and the filtrate and washing combined and cooled in an ice-bath. Water was added slowly with stirring and seeding until the product began to appear. Enough water was added to make the solution 3-4 N hydrochloric acid. The crystalline product was filtered ofl, washed with 3 N HCl, acetone and ether, and dried; yield 1.1 grams. This was crystallized two more times using the same procedure; yield 0.5 gram; small needle-like crystals, gray in color. This was the hydrochloride of dihydropteroylglutamic acid.

Analyses:

Calcd. for Found CnHnNrOaCI Per Cent The amount of hydrogen absorbed in the preparation of the compound was approximately equivalent to the amount calculated to be necessary to form a dihydro-derivative.

When the crystalline material described above was oxidized with alkaline potassium permanganate using just the amount calculated to be necessary to oxidize the dihydropteroylglutamic acid to pteroylglutamic acid a good yield of almost pure pteroylglutamic acid was obtained.

Example 2 Dihydropteroylglutamic acid has also been prepared by the following procedure: 2 grams of pteroylglutamic acid were dissolved in 150 cc. of a 1.5 N sodium hydroxide solution. 4.0 grams of zinc dust (containing 3% copper) were added, and the mixture stirred for thirty minutes. The zinc was filtered oif, the solution cooled to 10 C., and neutralized to pH 3.0. After cooling well the solid was collected, washed, and dried; yield 1.8 grams.

This was purified by the procedure described above, and the same compound was obtained. The ultraviolet adsorption spectra of this compound diifers markedly from that of pteroylglutamic acid. In .1 N NaOH pteroylglutamic acid has three maxima at 255 m 282 m and 365 my, whereas the dihydropteroylglutamic acid in .1 N NaOH has only one maximum at 285 my.

Other polyglutamic acid amides of dihydropteroic acid have likewise been prepared by reduction of suitable pteroylglutamates.

We claim:

A process which comprises mixing together and heating under non-oxidizing conditions, 2,4,5-triamino-6-hydroxypyrimidine, alpha,betadibromopropionaldehyde, and para-aminobenzoylglutamic acid.

COY W. WALLER. JOHN H. MOWAT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date ODell Mar. 13, 1951 OTHER REFERENCES Number 

